Aqueous processing waste treatment

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

Aqueous Eva.pora.tlon. Aqueous evaporation for hazardous waste treatment can be accompHshed in a closed process vessel that uses steam to evaporate the Hquid into a water vapor, which is ultimately condensed and may be reused, as shown in Figure 5. The concentrated Hquid is coUected for further treatment or disposal. 

An overview is presented of plutonium process chemistry at Rocky Flats and of research in progress to improve plutonium processing operations or to develop new processes. Both pyrochemical and aqueous methods are used to process plutonium metal scrap, oxide, and other residues. The pyrochemical processes currently in production include electrorefining, fluorination, hydriding, molten salt extraction, calcination, and reduction operations. Aqueous processing and waste treatment methods involve nitric acid dissolution, ion exchange, solvent extraction, and precipitation techniques. 

Waste Treatment. Figure 2 outlines the current waste recovery and treatment processes, and proposed changes. Acid waste streams are sent through nitric acid and secondary plutonium recovery processes before being neutralized with potassium hydroxide and filtered. This stream and basic and laundry waste streams are sent to waste treatment. During waste treatment, the actinides in the aqueous waste are removed by three stages of hydroxide-iron carrier-flocculant precipitation. The filtrate solution is then evaporated to a solid with a spray dryer and the solids are cemented and sent to retrievable storage. 

Wastewaters containing chlorinated hydrocarbons (CHCs) are very toxic for aquatic system even at concentrations of ppm levels [1] thus, appropriate treatment technologies are required for processing them to non-toxic or more biologically amenable intermediates. Catalytic wet oxidation can offer an alternative approach to remove a variety of such toxic organic materials in wet streams. Numerous supported catalysts have been applied for the removal of aqueous organic wastes via heterogeneous wet catalysis [1,2]. 

Cold-pressed essential oils from the peel are some of the most important by-products recovered during the processing of Citrus fruits. The presence of limonene in the aqueous discharges, with its antimicrobial activity [1], decreases the effectiveness of the waste treatment system and increases the time necessary for the biological breakdown of the organic matter produced in the peel oil recovery system [2,3]. Additional recovery of essential oils from waste water would increase industry s returns and reduce the pollution problems associated with the disposal of waste water [4,5]. Several methods for reducing the levels of residual essential oils in the aqueous effluent have been developed over the years [6-11]. 

The aqueous biphasic extraction technology also has potential for the treatment of process wastes that contain high concentrations of salts such as sodium carbonate, sulfate, or phosphate. 

Aqueous cyanide effluent containing a little methanol in a 2 m3 open tank was being treated to destroy cyanide by oxidation to cyanate with hydrogen peroxide in the presence of copper sulfate as catalyst. The tank was located in a booth with doors. Addition of copper sulfate (1 g/1) was followed by the peroxide solution (27 1 of 35 wt%), and after the addition was complete an explosion blew off the doors of the booth. This was attributed to formation of a methanol vapour—oxygen mixture above the liquid surface, followed by spontaneous ignition. It seems remotely possible that unstable methyl hydroperoxide may have been involved in the ignition process. See Waste treatment, below. 

Sonochemical reactors can be used to degrade a variety of contaminants in aqueous solution, including some very harmful and recalcitrant compounds such as chlorinated hydrocarbons. The scale-up of these reactors in order to meet industrial needs (i.e., faster rates and high volume processes) is the present challenge in the development of the technique. The many advantages of the technique, described in this chapter, will surely encourage researchers and engineers to face some unsolved problems in the future, in order to provide alternatives to conventional waste treatment. 

The liquid waste stream from the first step of the VX neutralization process at NECDF is called hydrolysate. Hydrolysate is the solution resulting from the treatment of the VX agent with an aqueous NaOH solution. It is a high-pH mixture that consists of two phases, aqueous and organic. The organic phase may represent up to 5 percent by volume of the total mixture. This hydrolysate process waste stream must be destroyed for compliance with the Chemical Weapons Convention treaty (NRC, 1998). Approximately 33 percent of the original VX stockpile at NECDF has been neutralized as of January 2007, resulting in the accumulation... 

Foam separation process involves the selective adsorption of the surface-active pollutants at the gas-liquid interfaces of fine air bubbles in a foam separation column. The surface-active pollutants, which are adsorbed on the surfaces of the rising bubbles, can be carried upward to the top of the foam separation column and thus removed from the aqueous system as condensed foam. Foam separation can be used for both waste treatment and water purification. This section presents the data on the feasibility of removing various organics and inorganics by the foam separation processes. A general survey of foam separation process and its fundamental principles are also presented. 

Chlorine in elemental or hypochlorite salt form is a strong oxidizing agent in aqueous solution and is used in water treatment for disinfection, and in industrial waste treatment facilities primarily to oxidize cyanide. Chlorine and hypochlorites can also be used to oxidize phenol-based chemicals, but their use is limited because of the formation of toxic chlorophenols if the process is not properly controlled. 

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